363-206-295
Circuit Pack Descriptions
Issue 1
December 1997
7-43
On the BBG12 3STS1E side, the EC-1 inputs from an STSX-1 cross-connection
panel are sent to both the active and standby BBG12 3STS1E circuit packs. Only
the active unit selects the EC-1 input. The SYSCTL circuit pack supervises the
state of the active and standby units so that the relay state of each is always the
inverse of the other. The hybrid on the active unit splits the EC-1 input signals and
sends them to the standby unit and to its own receiver. To implement a protection
switch on the EC-1 side, the SYSCTL switches the relays on each unit to their
opposite state.
When a BBG12 3STS1E is removed, shorting contacts on the backplane
connector operate so that the EC-1 input signal from its companion unit is
returned for proper termination.
Fault Detection Circuitry
7
Monitoring and Testing.
7
The BBG12 3STS1E circuit pack has in-service and
out-of-service built-in test capability. In-service testing is continuous, and errors
are reported when they occur to the SYSCTL via the intra-shelf control bus. An
out-of-service test is performed whenever the BBG12 3STS1E circuit pack is
inserted or recovers from a transient failure.
Loopbacks.
7
Two loopbacks (terminal and facility loopbacks) are provided on the
BBG12 3STS1E circuit pack. The terminal loopback (STS-1 loopback) loops the
incoming STS-1 signal back toward the TSI circuit pack. The facility loopback
(STSX-1 loopback) loops the incoming EC-1 signal back toward the STSX-1
cross-connection panel.
Power Circuitry
7
The BBG12 3STS1E circuit pack receives two sources of
−
48 volts that are in turn
diode ORed, fused, and filtered before conversion to +5 volts to power the rest of
the circuit pack. A failure of the fuse or converter causes the red FAULT LED to
light.
